Description: This is one of the larger headed species, solitary or clustering when the main head is about 5-7 cm in diameter and producing a nice patch over time. It distinguish for for the tubercles with chinned bases. Remarks: This Taxon has lots of synonyms ( like many other cacti) whit several controversial varieties and subspecies and comprises a multitude of different forms, but where each form is linked to others by populations of plants with intermediate characteristicsRoots: It has long tap roots.Stem: Fresh green in colour, flattened globular, hemispherical or shortly cylindrical, depressed at apex, 9-10 cm tall 6-7 cm in diameter. This species pups at the base. Ribs: About 20, tuberculate, spiralling; tubercles with chinned protrusions.Areoles: Elongate, 5-7 mm. Central spines: 2-4 or more. 5-35 mm long.Radial spines: 14-18, 5-25 mm long, comb-like and ascending, yellow, reddish, dark brown or black (mostly mahogany red-brown o black spines in subsp. mentosa). Flowers: Showy that cluster around the lower stem, funnel-shaped with short necks, about 3 cm tall, 3,5 cm in diameter, deep purple or magenta. Blooming season: Spring.Fruit: Dark reddish-brown with pale green scales.

Subspecies, varieties, forms and cultivars of plants belonging to the Rebutia mentosa group

Cultivation and Propagation: Sulcorebutias are summer grower species easy to cultivate, more cold tolerant than most. These mountainous plants have thick taproots and are susceptible to overwatering. They requires also an appropriate air circulation and are sometime grafted to avoid root problems. Growth rate: It is a relatively rapidly growing and easily flowering species. It's a heavy clumper and produces a nice patch over time.Soils: It likes very coarse mineral cactus mix soil, but can become too elongated if compost is too rich.Repotting: Use pot with good drainage.Watering: Water regularly from Spring to Autumn, but do not overwater(Rot prone), it must be strictly kept dry throughout the winter quiescent period since it is very sensitive to any moisture excesseskeep dry in winter. Fertilization: Feed with a high potassium fertilizer in summer. Hardiness: They need to be kept in a cool place during winter rest and are somewhat resistant to frost if kept on the dry side prior to, and during, cold weather (due to the altitude they are hardy to -7 C ° C, or less for short periods). The cold is important for the flowers, as well as for their health. Without this cool winter period, they normally won't get any buds.Exposition: Requires full sun or light shade and careful watering to keep plant compact with strong coloured spines. Tends to bronze in strong light, which encourages flowering and heavy spine production. Light shadow my be useful in the hottest summer days.Uses: It is an excellent plant for container growing. It always looks good and stays small. It look fine in a cold greenhouse and frame or outdoor in a rockery.Pests & diseases: It may be attractive to a variety of insects, but plants in good condition should be nearly pest-free, particularly if they are grown in a mineral potting-mix, with good exposure and ventilation. Nonetheless, there are several pests to watch for: - Red spiders: Red sopiders may be effectively rubbed up by watering the infested plants from above.- Mealy bugs: Mealy bugs occasionally develop aerial into the new growth among the wool with disfiguring results, but the worst types develop underground on the roots and are invisible except by their effects. - Sciara Flies: Sciara flies are one of the major problems for seedlings. It is a good practice to mulch your seedlings with a layer of grit, which will strongly discourage the flies. - Scales: Scales are rarely a problem.It is wise to treat your whole collection with a systemic insecticide twice a year in spring and autumn. - Rot: Rot is only a minor problem with cacti if the plants are watered and “aired” correctly. If they are not, fungicides won't help all that much. To prevent rottenness it is also advisable to surround its root neck by very rough sand or grit, this help a fast water drainage.Propagation: Seed, cutting, grafting. Seeds germinate in 7-14 days at 21-27° C in spring, remove gradually the glass cover as soon the plants will be well rooted (ca 1-2 weeks) and keep ventilated, no full sun for young plants!